Method of producing riddled thermoplastic sheets



F. R. NISSEL Sept. 21, 1954 METHOD OF PRODUCING RIDDLED THERMOPLASTIC SHEETS Filed April 25, 1951 A T 7/ /1556 Pom/7's INVENTOR FRANK R. NISSEL BY ATTORNEY Patented Sept. 21, 1954 METHOD OF PRODUCING RIIIDLEII- THERMOPIJAS TIC SHEET S" Frank-Ralph NisscL- Plainfieldgi N. J2, assignorctoe Unionte'arhide .amlL CarbonrGomporation; admin, poration of NewYork Original application September 8, 1949, Serial No;-1-14;604z- Divided and thisapplibatldn April 25 1951; Serial N0i=222,893 l ='Claims.-

1:; Thisrinvention IBIMEQSwtOiLaII jmproveeli'methodc 01 riddling thermoplastic: sheet or tow-be:

used for wearing aapparelg: up'holsteryrand zrtheslikea sure: thereon .With; 8111185311: screen; or, -.a hard-i sun;- face engravedwith Kai-screen pattern- 1 can pro duce; a: riddled filmnor sheetwith as many; as; 3600: perforations perwsquare' inch; Simultaneeously with the perforation thereof, thEsSGIEBBHE patternv is embossedvon i thesurface of thefilnrpr: sheet; givingiitauwovenappearance inzeither reeflecteclorv transmittede light; The: perforationsare -evenly spaced zthneughou-t 'thetipattern, being;

enhance the-Woven appearance in -transmitted Ifii formed? bythe evenly spaced inter-sectionsbf the light. Wire; and:arewsubstantiallyyuniiormein LSIZB: As.

Another ob'ject is to provide a riddled thermothe:thermoplastic.materiah=has:been=:forced; out: plastic sheet or film with smooth, clean-cut edges of the perforated zareae whileeat a-tvtemperature on the perforations-therein and; Where desirable," abovei its-softening; thea-edgQS-of: the per-.-- with perforations of-a-size sufiici ent' to permitthe v forations-are fused :andismooth; Nciasee edge-s' ready passage of air 'but-insufficient to: permit the.

ready passage of water.='

A further object is to provide. an. improved;

terials have thedisadvantage, however; ofbeing .v

unable to breathe, i. e; they are -almostcom'- pletely impervious to air and water vapor, and: for some purposesare thereby rendered less comfontableto the weareroruuser than woven fabrics on leather.

remain :to blocktheeperforation' and: reduce-the ventilating efiect, a In -2 1,drlition-, v where other than. the coarsest screen is used theriabric has anim-- proved .hand-. i." eciitano-zrlonger; possesses the cold smooth-feeling; characteristic-of i theeune 2 approximately equal; tocthe. :threadidiameter of that \fabrici If coarser materials such as --those= of the woven .reed.-.ty pe,- are toze-beisimulated a screen with asmall number: of meshes per; inch, whereinnthetwire diameter. is only a..fraction.. of l the intrstice width, should'be employed. By

It has previously been proposed to riddle theremp glewrimpedrscreen i'n ,placeofdoumoplastic film or sheet solely by mechanical permpeolLscreen oflidnt a m s r e sam foration erg. by piercing. thev materialfwith a c-like appearance may be achieved wit p sharp; pointed object; Mechanical perforation of l p mately, one-half. ithetpe o y; a this nature leaves. jagged edges around) the t t t W re n s n l wri mpedscreen eme perforations which have ajenden y t Subseboss thematerial. without "perforating it. Thus, quently block-the-opening andwdestroy the-venit pp nt-that many/and lvariledefiectscall tuatin efiect It has alsobeen proposed-t0 be achieved inlpracticing:my inventionby-varyingz foratethermoplastic resinous..material by dise the meshes per inchwiresd'iametel" and flrimllof changinggan'electricarctherethroughi Suchelecethe screenemployed" trot-perforation is limitedin the-; perforation den Eormanruses g! m m 51W; obtainable. because of tendency: of des1rable that the riddled material be impervious, area-to short-cireuit? through'anymea-rby;hole: to Water' hasmeen determined perfola" ith ofrthesepmethods th appgarance: f; tions of:0'.002inch:=diameter"oriless will: prevent the-.atreatedi material andz anyysubsequent :emi-v passage Watelbnot under Substantial Pre bossingi; thereof greatlyj reduces: the. ventilating; Sure; The screen which pr du es w perforationv effect by filling upjmanygofthe 'perforationss 0 0- inch; me e w m p y d 111: the

I-havediscovered that by'heating thezthermopractice of this invention wilh varyysomewha-t plastic resinousvmaterialrtaa temperature above with the thickness .of thethermoplastic: material its-softening point and: exertingsufiicient pres and thediameter ot-thewineused, For example with thermoplastic film up to 0.012 inch thick, standard wire screen of from 60 to 20 meshes per inch of wire 0.006 to 0.015 inch in diameter will produce that size hole. With thermoplastic sheeting of from 0.012 to 0.020 inch thick, wire screen of from 25 to meshes of wire 0.010 to 0.030 inch in diameter will produce a 0.002 inch diameter hole. Increased material thickness requires increased screen wire diameter to produce a perforation of a given dimension under otherwise similar conditions. The wire diameter must always be at least one half the thickness of the thermoplastic to be riddled, thereby enabling the intersecting wires of the screen to completely penetrate the material.

A riddled thermoplastic film material of a thickness up to 0.012 inch with a cloth-like appearance may be made by employing screen from approximately 60 to 20 meshes per inch of wire 0.006 to 0.015 inch in diameter. With slightly plasticized or unplasticized thermoplastic sheeting, even coarser screen may be used. For example, 0.020 inch thick sheeting when riddled with 20 meshes per inch screen of wire 0.022 inch in diameter has the appearance of woven reed material such as is used for automobile seat covers and the like. The maximum screen mesh which produces the desired ventilating effect and appearance with thermoplastic sheeting is about a 25 meshes per inch screen of wire 0.018 inch in diameter. The minimum screen mesh producing the effect is about 4 meshes per inch screen from wire 0.030 inch in diameter. This range is valid for sheeting from 0.012 to 0.020 inch thick. Where screen of less than 10 mesh per inch is employed, the riddled material, while well ventilated and embossed will not prevent water from passing therethrough.

A thermoplastic film 0.004 inch thick when embossed and riddled by my process with a 50 meshes per inch screen had a moisture transmission of 1031 grams/day/square meter. Similar film when riddled by an electric discharge process had a moisture transmission of 148 grams/ day/square 'meter. The moisture transmission was determined as follows: The riddled material to be tested was fastened in a relaxed condition over the mouth of an 80 mm. diameter, 40 mm. deep beaker containing 11 grams of calcium chloride. The beaker was weighed and placed in an atmosphere with a relative humidity of 100% (General Foods Humidity Cabinet) for 96 hours at 100 F. The beaker and sample of material were then reweighed and the moisture transmission calculated.

This invention may be practiced as a unit process or a continuous process. In the accompanying drawings:

Fig. 1 is a perspective view of the apparatus used in a unit process;

Fig. 2 is a perspective view of a modification of Fig. 1 wherein one plate, engraved with a screen design, is substituted for the screen and one plate shown in Fig. 1;

Fig. 3 is a perspective view of the apparatus used in a continuous process employing my invention; and

Fig. 4 is an enlarged partial cross-sectional view of Fig. 1 showing a plastic sheet ll perforated in areas adjacent to the interstices of the wires in the woven screen I2 which has been pressed into the plastic sheet by means of the opposed platens ID.

The material perforated and embossed in accordance with my invention has one smooth sur- 4 face and one surface with the appearance of a woven fabric. As the minute perforations are only readily visible in transmitted light they are not represented in the drawings.

In practice, one or both of the press plates 10 are heated to a temperature above the softening point of the thermoplastic material H. Pressure is then applied to the plates 10 forcing the screen [2 to simultaneously emboss and riddle the material H. The plates are then cooled and the ventilated material is stripped from the screen. As shown in Fig. 2, an engraved plate [3 may be substituted for the screen 12 and one plate l0 of Fig. 1.

In continuous operation, the thermoplastic material is preheated to above its softening point and fed between the smooth backing roll l4 and the screen engraved roll 15. These rolls may be left to find their own temperature but it is preferable that they be cooled somewhat by any known means in order to assist in reducing the temperature of the riddled material below its softening point as soon as possible after the riddling operation.

The following examples are illustrative of the practice of the invention but are not to be construed as limiting the scope thereof.

Example I Thermoplastic material Film of vinyl chloridevinyl-acetate copolymer Material thickness (inches) .004 Temperature C.) 165 Pressure (lbs/sq. inch) 600- Perforations (per sq. inch) 2500 Perforation diameter (inches)- .002 Moisture transmission (grams/ day/sq. meter) 1031 Example II Thermoplastic material Sheeting of vinyl chloride vinyl acetate copolymer Material thickness (inches) .020 Temperature C.) Pressure (lbs/sq. inch) 600 Perforations (per sq. inch) 400 Perforation diameter (inches) .003

Moisture transmission (grams/day/sq. meter) 291 This is a divisional application of my'copending application, Serial No. 114,604, filed September 8, 1949, now abandoned.

I claim:

1. Method of perforating and imparting a woven fabric appearance to thermoplastic film or sheet material, which comprises heating the thermoplastic film or sheet material to above its softening temperature, positioning the heated material between a smooth backing surface and an embossing means having a woven wire pattern in which pattern the wire diameter is at least half thethickness of the thermoplastic material, applying sufficient pressure for the wire pattern to be embossed on the thermoplastic material and to perforate through the thermoplastic material at all the wire intersections in the woven pattern surface, and then stripping the perforated and embossed material from the pattern.

2. Method of perforating and imparting a woven fabric appearance to thermoplastic resinous material which comprises heating said material in sheet or film form to a temperature above its softening point, pressing said material between a smooth backing plate and a woven wire screen of from 60 to 4 meshes per inch, the diameter of said wire being at least half the thickness of the thermoplastic sheet or film, at a pressure sufficient to cause said screen to perforate said material at each intersection of the wires of said screen, cooling said material to below its softening point and stripping it from the screen.

3. Method of perforating and imparting a woven fabric appearance to thermoplastic resinous film material of less than 0.012 inch thickness which comprises heating said material to a temperature above its softening point, pressing said material between a smooth backing plate and a woven wire screen of from 60 to 20 meshes per inch, the diameter of said wire being at least half the thickness of said film material, at a pressure sufficient to cause said screen to perforate said material at each intersection of the wires of said screen, cooling said material to below its softening point and stripping it from the screen.

4. Method of perforating and imparting a woven fabric appearance to thermoplastic resinous sheet material of from 0.012 to 0.050 inch thickness which comprises heating said material to a temperature above its softening point, pressing said material between a smooth backing plate and a woven wire screen of from 25 to 4 meshes per inch and having a wire diameter at least half the thickness of the sheet material, at a pressure sufficient to cause said screen to perforate said material at each intersection of the wires of said screen, cooling said material to below its softening point and stripping it from the screen.

5. Method of perforating and imparting a woven fabric appearance to thermoplastic resinous material which comprises heating said material in sheet or film form to a temperature above its softening point, applying pressure to said material by means of a smooth backing plate and an engraved facing plate, said facing plate being configurated as a woven wire screen of from 60 to 4 meshes per inch and having a wire diameter at least half the thickness of said sheet or film. and said pressure being sufficient to cause said screen configuration to perforate said material at each intersection of said screen configuration, cooling said material to below its softening point and stripping it from the screen pattern.

6. Method of perforating and imparting a woven fabric appearance to thermoplastic resinous film material of less than 0.012 inch thickness which comprises heating said material to a temperature above its softening point, applying pressure to said material by means of a smooth backing plate and an engraved facing plate, said facing plate being configurated as a woven wire screen of from 60 to 20 meshes per inch and with a wire diameter of at least half the thickness of the film, and said pressure being sufficient to cause said screen configuration to perforate said material at each intersection of said screen configuration, cooling said material to below its softening point and stripping it from the screen pattern.

7. Method of perforating and imparting a woven fabric appearance to thermoplastic resinous sheet material of from 0.012 to 0.050 inch thickness which comprises heating said material to a temperature above its softening point, applying pressure to said material by means of a smooth backing plate and an engraved facing plate, said facing plate being configurated as a woven wire screen of from 2'5 to 4 meshes per inch and with the wire diameter being at least half the thickness of the sheet material, and said pressure being sufficient to cause said screen configuration to perforate said material at each intersection of said screen configuration, cooling said material to below its softening point and stripping it from the screen pattern.

8. Method of perforating and imparting a woven fabric appearance to thermoplastic resinous material which comprises heating said material in sheet or film form to a temperature above its softening point, pressing said material between a hard backing roll and an engraved facing roll, said facing roll being configurated as a woven wire screen of from 60 to 4 meshes per inch and with the wire diameter being at least half the thickness of said sheet or film, and said pressure being sufficient to cause said screen configuration to perforate said material at each intersection of said screen configuration, and continuously stripping said material from said facing roll.

9. Method of perforating and imparting a woven fabric appearance to thermoplastic resinous film material of up to 0.012 inch thickness which comprises heating said material to a temperature above its softening point, pressing said material between a hard backing roll and an engraved facing roll, said facing roll being configurated as a woven wire screen of from 60 to 20 meshes per inch and with a wire diameter at least half the thickness of said film material, and said pressure being sufiicient to cause said screen configuration to perforate said material at each intersection of said screen configuration, and continuously stripping said material from said facing roll.

10. The process of riddling thermoplastic resinous sheet material of from 0.012 to 0.050 inch thickness which comprises heating said material to a temperature above its softening point, pressing said material between a hard backing roll and an engraved facing roll, said facing roll being configurated as a woven wire screen of from 25 to 4 meshes per inch and with a wire diameter at least half the thickness of the thermoplastic sheet material, and said pressure being suificient to cause said screen configuration to perforate said material at each intersection of said screen configuration, and continuously stripping said material from said facing roll.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,032,935 Hurt Mar. 3, 1936 2,032,941 Linscott Mar. 3, 1936 2,070,023 Olsen Feb. 9, 1937 2,446,771 Knowland Aug. 10, 1948 

